August 19, 2013
Exoplanet Discovered That Makes Full Orbit In Under Nine Hours
Lee Rannals for redOrbit.com - Your Universe Online
Scientists from MIT have discovered an exoplanet 700 light-years away that fully orbits its host star every 8.5 hours.The scientists wrote in The Astrophysical Journal the earth-sized planet, Kepler 78b, has one of the shortest orbital periods ever detected. They have estimated its surface temperatures may reach more than 5,000 degrees Fahrenheit due to its extremely close orbital position.
Kepler 78b is so close to its star the researchers believe scientists will be able to measure its gravitational influence on the star. This data could be used to help measure the planet's mass, which would make it the first Earth-sized planet outside of our Solar System to have its mass measured.
They analyzed light data from thousands of stars while looking for "dips" in the star light data. This dip occurs when an object passes between the star and the telescope.
The researchers were able to detect light being emitted by the planet for the first time. The light may give scientists information about Kepler 78b's surface composition and reflective properties. The team was able to detect the light given off by the planet by measuring the amount by which the overall light dimmed each time the planet passed behind the star.
“I was just looking by eye, and all of a sudden I see this extra drop of light right when it was expected, and it was really beautiful,” said physics graduate student Roberto Sanchis-Ojeda. “I thought, we’re actually seeing the light from the planet. It was a really exciting moment.”
According to the findings, the planet's light seen in the Kepler telescope data could be a combination of radiation from its heated surface and light reflected by surface materials, such as lava and atmospheric vapor.
The team looked through more than 150,000 stars that were monitored by the Kepler Space Telescope, hoping to find Earth-sized planets with short orbital periods.
“We’ve gotten used to planets having orbits of a few days,” says Josh Winn, an associate professor of physics at MIT. “But we wondered, what about a few hours? Is that even possible? And sure enough, there are some out there.”
Kepler 78b is about 40 times closer to its star than Mercury, which is the closest planet to our sun. The scientists surmise the exoplanet's star is relatively young because the star rotates more than twice as fast as the sun, which is a sign it has not had much time to slow down.
Winn and colleagues published a separate paper in Astrophysical Journal Letters of a previously discovered exoplanet with an even shorter orbital period of just 4.25 hours. The team determined in order for the planet to maintain its extremely tight orbit around its star it would have to be incredibly dense, made up almost entirely of iron.
“Just the fact that it’s able to survive there implies that it’s very dense,” says Winn. “Whether nature actually makes planets that are dense enough to survive even closer in, that’s an open question, and would be even more amazing.”
NASA's Kepler Telescope completed its primary mission last year, but experienced a failure back in May that caused the exoplanet hunting tool to stop working. The space agency launched a final "Hail Mary" attempt to try and get the telescope back online, however NASA said last week it has ended attempts to fully recover Kepler.
"Kepler has made extraordinary discoveries in finding exoplanets including several super-Earths in the habitable zone," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "Knowing that Kepler has successfully collected all the data from its prime mission, I am confident that more amazing discoveries are on the horizon."